Abstract: A device and method for measuring and correcting eye aberrations integrate wavefront sensing, wavefront aberration correction and optometric testing into one another and configure the optical paths of wavefront sensing and optometric testing as aplanatic structures, such that under optometric testing conditions both wavefront sensing and aberration correction can be performed simultaneously, and final optometric testing is conducted on wavefront aberration-corrected optometric parameters to verify if the wavefront aberration-corrected optometric parameters fall within normal visual range, thus ensuring the accuracy and high repetition of the measured optometric parameters.

Abstract: A sighting device for an examination by in vivo tomography of an eye of a subject including a viewer controlled by a control system for displaying at least one moving target where the at least one moving target has at least one of a programmable shape and a programmable trajectory, and is visible by the eye of the subject during the examination period to allow the subject to fixate and follow the target with their eye.

Abstract: There is disclosed an ophthalmic apparatus including a detection unit which detects a vision fixation state of an eye to be examined, a projection unit which projects a fixation mark onto a fundus of the eye, and a fixation mark control unit which controls the projection unit. The projection unit includes a changing unit which changes a fixation mark to be projected onto the fundus, and when a vision fixation state detected by the detection unit does not satisfy a predetermined criterion, the fixation mark control unit controls the changing unit to change a fixation mark to be projected onto the fundus.

Abstract: An instrument for measuring a refractive power includes a target, a target projecting unit, a measurement light projecting unit, a light receiving unit, a unit for performing a normal refractive power measurement, a judgment unit, and a unit for performing a high-speed refractive power measurement. The unit for performing a normal refractive power measurement measures a normal refractive power of an examined eye based on received light data. The judgment unit judges reliability of the received light data or the refractive power measurement. The unit for performing a high-speed refractive power measurement measures a refractive power of the examined eye faster than the unit for performing a normal refractive power measurement in response to a judgment result of the judgment unit.

Abstract: In a laser eye treatment apparatus, a probe light source generates a secondary emitted light emanating from a treatment area of retinal tissue that is irradiated by a treatment light source. An optical detector detects the secondary emitted light. A processor statistically analyzes the secondary emitted light to determine a temperature of the treatment area of retinal tissue.

Abstract: Devices, systems, and methods measure, diagnose, and/or treat one or both eyes of a patient. Adaptive optics systems (such as those having a deformable mirror) may be configured to an aspherical or multi-spherical presbyopia-mitigating prescriptive shape to allow objective and/or subjective measurements of a candidate prescription. A plurality of viewing distances allow subjective and/or objective evaluations of performance using a light spot or a test viewing image. Measurements of aberrations at selected viewing conditions (including distances and/or brightness) with correlating pupil sizes may also be provided. Wavefront measurement systems and methods may help position and isolate the eye from ambient light.

Abstract: An apparatus for obtaining a retinal image of an eye has a control logic processor (214) for executing a sequence of operations for obtaining the image. A visual target (162) orients the eye of a patient when viewed. An indicator element (410) provides a signal that indicates that the patient is in position. A cornea focus detection section (450) indicates cornea focus, in cooperation with the control logic processor (214). An alignment actuator aligns the optical path according to a signal obtained from the cornea focus detection section (450). A retina focus detection section (452) detects retina focus in cooperation with the control logic processor (214). A focusing actuator (406) is controlled by instructions from the control logic processor (214) according to a signal obtained from the retina focus detection section (452). An image capture light source is energized by the control logic processor (214) for illuminating the retina.

Abstract: Systems and methods for measuring a distance from a reference plane of an optical measurement instrument to a reference plane of an optical device under test are disclose. In one embodiment a system for measuring this distance includes an illumination system, an optical system, and optical sensor and a processor. The illumination system is configured or adapted to illuminate the object under test. The optical system is configured or adapted to receive light from the object under test and to produce an aberrated image. The optical sensor is configured or adapted to receive and sense the aberrated image. The processor determines the distance from the reference plane of the optical measurement instrument to the reference plane of the optical device based on an aspect of the aberrated image sensed by the optical sensor.

Abstract: An apparatus and method for treating and/or diagnosing a patient's eye. A light source produces fixation light and procedure (treatment and/or diagnosis) light. A scanning device deflects the fixation light to produce a fixation pattern of the fixation light on the eye, and deflects the procedure light to produce a procedure pattern of the procedure light on the eye. A controller controls the scanning device such that the fixation and procedure patterns move relative to each other, and/or the fixation pattern dynamically changes.

Abstract: An apparatus and method for treating and/or diagnosing a patient's eye. A light source produces fixation light and procedure light. A scanning device deflects the fixation light to produce a fixation pattern of the fixation light on the eye, and deflects the procedure light to produce a procedure pattern of the procedure light on the eye. A controller controls the scanning device such that the fixation and procedure patterns move relative to each other, and/or the fixation pattern dynamically changes.

Abstract: A sequential wavefront sensor comprises a light beam scanning module, a sub-wavefront focusing lens, a detector with more than one photosensitive area and a processor for calculating the sequentially obtained centroids of a number focused light spots from the sub-wavefronts to determine the aberration of the input wavefront. A sequential wavefront sensing method comprises the steps of; sequentially projecting a number of sub-wavefronts onto a sub-wavefront focusing lens and a detector with more than one photosensitive areas, calculating the centroid of the focused light spot from each sub-wavefront, and processing the centroid information to determine the aberration of the wavefront.

Abstract: A contrast chart device of the present invention comprises a contrast target presenting part for presenting a contrast target for a contrast sensitivity test at prescribed timing; a pupil data measuring part for producing an image of an anterior ocular segment of a subject and measuring the diameter or area of a pupil region in the anterior ocular segment; and a measurement timing forming part for forming timing at which the pupil data measuring part performs measurement.

Abstract: A sighting device is provided for an examination of the eye, including at least one moving target with a programmable form and trajectory, the target being displayed on a visualisation unit, such as an appropriate screen and visible from both eyes during the examination. An in-vivo tomographical eye examination system is also provided, including: a Michelson interferometer, generating a full-field OCT image, adaptable optical apparatus, arranged between the interferometer and an eye for examination, achieving the correction of the wavefronts coming from the eye and also the wavefronts going to the eye, detection apparatus, arranged after the interferometer, permitting the interferometric measurement by the OCT principle without modulation nor synchronized detection and a sighting device, with at least one mobile target with a programmable form and trajectory, the target being displayed on an appropriate screen and visible from at least one of the eyes during the examination.

Abstract: An optical image measurement device has: an interference-light generator configured to generate an interference light by splitting a low-coherence light into a signal light and a reference light and superimposing the signal light having passed through an eye and the reference light having passed through a reference object; a detector configured to detect the generated interference light; and a scanner configured to scan a projection position of the signal light on the eye, and the optical image measurement device is configured to form an image of the eye based on a result of detection by the detector. The optical image measurement device comprises a projector configured to project fixation information for fixing the eye onto a fundus oculi of the eye when the scanner scans with the signal light.

Abstract: The invention concerns a device for displaying an image directly on the retina (6) of the eye (5). The device comprises means (1) arranged to emit laser radiation and modulating means (2) arranged in the beam path between the laser-radiation-emitting means (1) and the eye (5) so as to modulate the laser radiation. The device is characterized in that the modulating means (2) are arranged so as to modulate the phase front of the laser beam so that, when it strikes the refracting elements of the eye, it is deflected in a direction distinct from the direction obtained with unmodulated radiation. The invention also includes a method of displaying a retinal image.

Abstract: The invention relates to a device, for measuring the contrast of fringes in a Michelson interferometer at full field, comprising a Wollaston prism for diverting two perpendicular incident polarisations into two different emergent directions, said diverting means being arranged within the interferometer as substitute for a single polariser. The device is of application to a Michelson interferometer used in an OCT tomographical system and comprising means for obtaining interferometric contrast without use of a modulation technique or synchronous detection methods.

Abstract: A ophthalmic aberrometer uses a wavefront sensor aligned with an eye under examination through an optical path and a light source for introducing a light beam into the eye via the optical path, wherein the optical path has a reference through which the light beam passes before passing to an eye retina to form a reference spot on the retina, a focus dynamic range extender, and an astigmatism dynamic range extender positioned in the optical path between the reference and an eye under examination. The wavefront sensor is positioned to receive a wavefront reflected from the eye retina via the optical path.

Abstract: An eye refractive power measurement apparatus capable of measuring even an eye with a small pupil diameter with accuracy and stability. The apparatus has a measurement optical system including a projection optical system, having a light source, for projecting spot-shaped measurement light onto a fundus and a photo-receiving optical system, having a photodetector, for photo-receiving the measurement light reflected from the fundus via a peripheral pupillary portion, a calculation part which obtains the eye reflective power based on an output from the photodetector, alight deflection member, an arrangement of which in the measurement optical system being prevented from having a positional relationship optically approximately conjugate with a pupil, and a rotation unit which rotates the light deflection member about a measurement optical axis of the measurement optical system.

Abstract: The present invention contemplates an ophthalmic adaptive-optics instrument to obtain patient-verified prescription of low and high-order aberrations. The present invention further contemplates a new and improved method and apparatus of customized corneal ablation using a patient-verified prescription of low and high-order aberrations. The patient-verified prescription of high-order aberrations characterizes the aberration correction needed for optimal visual acuity and enables customized corneal ablation to achieve optimal visual acuity for each individual patient.

Abstract: The optometry apparatus includes an index projecting optical system for projecting an index for cross cylinder test to an eye for shortening examination time, a variable cross cylinder lens disposed on an optical axis of the index projecting optical system, for forming one pair of projection images of the index by switching of an astigmatic axial angle while predetermined astigmatic power is set, a joystick lever and a button used to input a result of comparison between appearance states of the pair of projection images of the index, and an initial value setting unit for determining an astigmatic axial angle of the variable cross cylinder lens to cause one of the pair of projection images of the index visually recognized and to cause the other thereof in a blurred state based on objective values of astigmatic power and an astigmatic axial angle of the eye, measured in advance, and for setting the determined astigmatic axial angle as an initial value for astigmatic axial angle measurement.

Abstract: A method for measuring the dynamic behavior of an optical system is aimed at rendering the dynamic behavior of the optical system objectively detectable. To this end, the optical system to be measured is stimulated by stimuli whereby causing it to react, and the reaction is detected by means of a wave front analysis.

Abstract: Apparatus and methods are provided for reducing or eliminating the progression of myopia, including a lens having an intentionally created aberration pattern for reducing or eliminating the progression of myopia. The aberration pattern may comprise a positive spherical aberration that produces a wavefront error in which the paracentral wavefront is disposed in front of the retina, thereby producing a signal that counters axial length growth of the eye and preventing the progression of myopia.

Abstract: In embodiments of optical arrangements of a working distance sensor in a fundus camera that can improve the determination of a correct working distance as well as the transverse positioning of the camera a number of near infrared light sources are arranged to project a number of near infrared illumination beams into the visible light illumination path of the fundus camera and a live view of the retina under near infrared illumination is captured and displayed on a monitor. These embodiments of optical arrangements and associated methods will enable an operator to directly determine if there is any undesirable flare or other artifact appearing within a designated region on the infrared retina view as a result of a wrong alignment of the fundus camera with respect to the eye in terms of not only the working distance but also the horizontal and vertical positions. Pattern recognition algorithms can be used to further enhance the positioning sensitivity of the working distance sensor.

Abstract: A corneal measurement apparatus for measuring a subject's cornea, comprising (A.) an illumination projection subsystem comprising a light source (B.) a mask subsystem disposed in a path of light from the light source, comprising (i) a first slit mask defining a plurality of apertures, (ii) a second slit mask defining a selection aperture, (iii) a translation apparatus adapted to translate the second mask, the translation apparatus and the second slit mask being configured and arranged such that by translating the selection slit, portions of the light can be selectively transmitted through each of the plurality of apertures toward the cornea, (C.) an imaging element configured and arranged to image the plurality of apertures onto the cornea, and (D.) an image capture subsystem arranged to capture images of the portions of light after the light impinges on the cornea.

Abstract: A system for testing a subject's cognition and motor timing includes an actuator, a sensor and a computer. The actuator is configured to present to the subject multiple stimuli, including predictable stimuli and non-predictable (e.g., random or pseudo-random) stimuli. The sensor generates sensor signals associated with the subject responding to the stimuli. The computer stores timing values associated with the sensor signals for a plurality of the sequences of stimuli, and analyzes the timing values to determine if the subject has an anticipatory timing impairment. The system may also be configured to provide feedback signals to the user, in which case the system also functions as cognition timing and motor training system.

Abstract: The invention is directed to an arrangement and a method for measuring the anterior segment of the eye using interferometric means. The eye is illuminated by a convergent beam bundle and aligned with the optical axis of the measuring device by generating directional stimuli and accommodation stimuli by means of a display which is mirrored into the beam path.

Abstract: To provide an ophthalmic apparatus capable of measuring plural different eye characteristics while avoiding a misjudgment. The apparatus includes an intraocular pressure measurement part having a blowing unit, an optical characteristics measurement part, a main body having the above measurement parts, a measurement part shifting unit bringing one of the measurement parts to a measurable state, a working distance detecting unit having a projection optical system and a photo-receiving optical system, a control part judging whether to continue shifting the intraocular pressure measurement part to the measurable state based on a detection result and controlling the shifting unit based on a judgment result, and a detection unit directly or indirectly detecting whether light photo-received on the photo-receiving optical system is target light reflected from a cornea, wherein when the light is not the target light, the control part judges it proper to continue shifting and controls the shifting unit.

Abstract: An ocular depth dimension measurement apparatus capable of accurately obtaining an ocular depth dimension. The apparatus has a measurement light projecting optical system with a light source which is arranged to make a part of the light from the light source into first and second measurement light and collect the respective measurement light on first and second measurement surfaces of the eye, an interference optical system with a separation unit arranged to make the light into reference light and an optical path length changing unit which is arranged to synthesize the first and second measurement light respectively with the reference light to make them interfere with each other so as to photo-receive and obtain interference signals of the respective interference light, and a calculation part arranged to calculate the ocular depth dimension based on the interference signals and a driving result of the changing unit.

Abstract: A subject (12) observes an image on a display (10). A control (18) produces a fixation image at a selected position in the display, followed by a stimulus spaced from the fixation image. An eye position sensor (14) detects a saccade movement towards the stimulus. The stimulus is then replaced with a fixation image and the cycle repeated. The time taken to saccade plus the intensity of the stimulus are used to produce a retinal map of field of vision, or to assess other characteristics of the subject.

Abstract: An ophthalmic measurement apparatus which measures wavefront aberration of a patient's eye with high accuracy includes an irradiation optical system including a high-coherence measurement light source, a photo-receiving optical system including a light dividing element and a photodetector, a measurement light deflector placed in a position on an optical path of the irradiation optical system and not on that of the photo-receiving optical system, a memory storing deflection information and a pattern photo-received on the photodetector and associated with the information, and a control unit which drives the deflector to form patterns in different deflection states, controls the photodetector to photo-receive the patterns, reads out from the memory the information and the pattern, corrects the patterns based on their corresponding information by an amount of displacement of the read-out pattern with respect to a reference pattern, and performs addition to the corrected patterns so as to calculate the wavefront a

Abstract: A fundus camera, of which usability is enhanced while offering an excellent combination of automatic and manual photographing, includes a photographing optical system having a photographing optical axis, a movable focusing lens and an image-pickup element, alignment-state detection means, focusing-state detection means, a fixation target presenting unit where a presenting position of a fixation target is changeable between a reference position for photographing a central portion and a peripheral position for photographing a peripheral portion, a photographing starting switch, means for switching between a manual mode in which photographing is performed based on a signal from the switch and an automatic mode in which photographing is automatically performed.

Abstract: The present invention provides an eye accommodation function state measurement device which places only a small burden on the subject, allows confirmation of an intermediate measurement result, and is more conveniently used. The eye accommodation function state measurement device disposes an image at a plurality of positions by using an image moving mechanism, and measures the accommodation function state of the subject's eye at each position. The eye accommodation function state measurement device includes a control section (65) which provides a measurement suspension period (S6 to S10) in which the measurement is suspended. In the measurement suspension period, the eye accommodation function state measurement device calculates the eye accommodation function state (S7), displays the intermediate measurement result of the eye accommodation function state (S8), or transmits data from the control section (65) to an external storage section (69) (S9).

Abstract: An eye refractive power measurement apparatus capable of checking a presenting position (presenting distance) of a fixation target. The eye refractive power measurement apparatus has a measurement optical system for measuring eye refractive power of an examinee's eye, a fixation target presentation optical system for presenting a fixation target to the examinee's eye, a changing unit which changes a presenting position of the fixation target in a direction of an optical axis of the presentation optical system, a display, and a controller which controls to display a change of the presenting position as a diopter change on the display graphically.

Abstract: For magnifying a display of a portable device, the display is placed at a distance less than the distance of the normal near point to the eye (about 25 cm). However, the image will be blurred since the eye cannot focus the image onto the retina. To form a magnified image onto the retina, a positive lens is added in front of the eye. With a positive lens in front of the eye, and the device is placed closer than the near point to the eye, a viewer can see clearly the magnified display. A 2.5? (6.25 cm) display will be seen like a 32? (80 cm) display or even larger.

Abstract: An ophthalmic apparatus for examining and evaluating a visual function of an eye of a patient, includes: a presentation unit which presents an examination target to the patient's eye; a storage unit which stores therein subjective information obtained from the patient as to whether or not the patient can visually recognize the presented examination target; a calculation unit which calculates an objective evaluation value for the patient's eye using a fuzzy theory expressed as a probability function, based upon the stored subjective information; and an output unit which outputs the calculated evaluation value.

Abstract: An ocular accommodative function examination apparatus for examining an accommodative function of an examinee's eye, includes: a fixation target presenting optical system which presents a fixation target at a presenting position to the eye, the presenting position being changeable in a direction of a visual axis of the eye; a refractive power measuring optical system which measures refractive power of the eye; an analysis part which acquires variation or fluctuation in the refractive power of the eye gazing at the fixation target at a certain presenting position within a predetermined time based on a result of measurement by the measuring optical system, and determines tho accommodative function of the eye based on the acquired variation or fluctuation; a display part which displays a result determined by the analysis part; and a control part which controls presenting of the fixation target to perform at least one of simple examination for determining the accommodative function with respect to a first present

Abstract: The invention relates to a device for measuring the optical properties of an eye, comprising an optical signal generator and optical guide means leading from the optical signal generator in the direction of the eye to be examined, wherein the optical signal generator is adapted to project an image through an optical path comprising the optical guide means and onto a reflective structure in the eye to be examined, wherein the device is adapted to couple the optical guide means of the device to optical guide means of an optical medical instrument so that the optical path extends through the optical guide means of the optical medical instrument. Such an optical medical instrument can be formed by an operating microscope, a so-called split lamp or by a fundus camera.

Abstract: An ocular accommodative function examination apparatus for examining an accommodative function of an examinee's eye, comprises: a fixation target presenting optical system which presents a fixation target at a presenting position to the eye, the presenting position being changeable in a direction of a visual axis of the eye; a refractive power measuring optical system which measures refractive power of the eye and includes a light projecting optical system which includes a light source and projects examination light to a fundus of the eye and a light receiving optical system which includes a light receiving element and receives the examination light reflected from the fundus; an analysis part which acquires variation or fluctuation in the refractive power in a specified measurement meridian direction of the eye gazing at the fixation target at a certain presenting position within a predetermined time based on output of the light receiving element, and determines the accommodative function of the eye based on

Abstract: Various embodiments of methods and systems for improving and enhancing vision are disclosed. Adjustable lenses or optical systems may be used to provide adaptive vision modification. In some embodiments, vision modification may be responsive to the current state of the user's visual system. Certain embodiments provide correction of the subject's near and far vision. Other embodiments provide enhancement of vision beyond the physiological ranges of focal length or magnification.

Abstract: A fundus camera that performs alignment easily and efficiently, and photographing a fundus favorably. A fundus camera has a photographing part in which a fundus photographing optical system is arranged, a fundus observation optical system having a first image-pickup element which picks up an image of the fundus, an anterior-segment observation optical system having a second image-pickup element which picks up an image of an anterior-segment of the eye, a display unit capable of displaying the image of the fundus picked up by the first image-pickup element and the image of the anterior-segment picked up by the second image-pickup element, and a control part which obtains information on alignment of the photographing part with the eye and decides which of the image of the fundus and the image of the anterior-segment is to be displayed on the display unit.

Abstract: Certain embodiments of the present invention provide a method and system for using gaze detection to improve information display in a healthcare environment. Certain embodiments of a system include an eyewear headset for detecting a location of a user's gaze and a display for displaying information. Information on the display, such as images and/or data, is customized for the user based on the user's gaze. In an embodiment, the eyewear headset viewer projects information into the user's oculars for an individual information display. The system may also include a conflict resolution module for determining priority and control of the display among a plurality of users. In an embodiment, a function at the display may be triggered using a voice command, a gesture, and/or a gaze, for example.

Abstract: An eye refractive power measurement apparatus which is capable of measuring even an eye with a small pupil diameter and measuring a normal eye with a large enough pupil diameter with accuracy and stability. The apparatus includes a measurement optical system for photo-receiving measurement light from a fundus via a ring-shaped aperture arranged at an approximately conjugate position with a pupil by using a photodetector, a changing device for changing a size of the ring-shaped aperture on a pupillary surface to a size different in both inside diameter and outside diameter, and a calculation device for calculating the eye refractive power based on a photo-receiving result obtained by the photodetector.

Abstract: Scattering can be measured by using an optical system having a Hartman-Shack wave-surface sensor.

Abstract: A device for measuring eye characteristics, an operation device, and the coordinate origin and the coordinate axes of each eye are sufficiently related with one another. A measuring unit (111) measures eye optical characteristics based on a first light receiving signal from a first light receiving unit (23), and measures a cornea topography based on a second light receiving signal from a second light receiving unit (35). The measuring unit (111) also computes an ablation amount based on an aberration result.

Abstract: A first movement unit for moving a condensing position so that a light flux from a light source is condensed on a place close to a retina of a subject eye, and a second movement unit for optically moving a conversion member for condensing a light flux reflected by the retina and a light receiving part for receiving light fluxes can be independently driven and can be further driven by an operation of an operator. First, an arithmetic part adjusts a projection side and a light receiving side based on first signals from the light receiving part. In a case where an independent mode is selected, the projection side and the light receiving side are adjusted automatically or manually. Further, the arithmetic part measures a characteristic of the eye in accordance with adjusted measurement conditions.

Abstract: In a visual training device and a visual training method, different targets are displayed for right and left eyes, respectively, and refractivities of the right and left eyes are measured. Based on the measured refractivities of the eyes, positions of the targets displayed for the right and left eyes are moved in the directions of the respective optical axes. At the same time, the targets are moved so that the visual axes of the right and left eyes incline outward toward the end. The directions of the visual axes of the right and left eyes incline outward toward the end, so that it is possible to relax the strain of musculus ciliaris and relieve visual fatigue through short, effective training.

Abstract: Provided is an ophthalmologic image taking apparatus with which an image of the eye to be examined can be taken with an appropriate light intensity and at an appropriate gain. In the case where an observation of an eye to be examined is conducted when it is detected that an image taking switch is turned on, an image taking light source emits light after a lapse of a predetermined time. The predetermined time is a time required to completely switch a gain from a gain obtained by AGC to a fixed gain and a time which is not influenced by blinking of the eye to be examined.

Abstract: An ocular accommodative function examination apparatus for examining an accommodative function of an examinee's eye, comprises: a fixation target presenting optical system which presents a fixation target at a presenting position to the eye, the presenting position being changeable in a direction of a visual axis of the eye; a refractive power measuring optical system which measures refractive power of the eye and includes a light projecting optical system which includes a light source and projects examination light to a fundus of the eye and a light receiving optical system which includes a light receiving element and receives the examination light reflected from the fundus; an analysis part which acquires variation in the refractive power of the eye gazing at the fixation target at a certain presenting position within a predetermined time based on output of the light receiving element, and determines the accommodative function including a range of accommodation and HFC (a frequency of occurrence of a high f

Abstract: An improved sequential scanning method and apparatus for measuring wavefront aberration involves angularly displacing a measurement beam from a parallel beam striking the corneal surface at a desired location and using the displacement of an image on a detector between the angularly displaced beam and a reference beam to obtain a more accurate wavefront measurement than provided by the displacement between the parallel beam and a reference beam conventionally used for such wavefront aberration measurement. A method and related apparatus for determining a retinal topography relies on using the improved measurement method and apparatus in conjunction with other ocular data to determine changes in the bulbous length of the eye based upon retinal image displacement.

Abstract: The present invention contemplates to employ an eye-tracking device in an ophthalmic adaptive-optics system such that slow wavefront sensor and aberration-compensating element can be sufficient for the application. The present invention further contemplates to implement with the eye-tracking device a motion-compensating mechanism into the system such that the pupil images on both the wavefront sensor and the aberration-compensating element remain stationary during the operation of the system.